Pickling bath for metals



Patented Apr. 10, 1945 2,273,291 PIGKLING Barn non METALS Charles 0.Clark, Buflalo, N. Y., assignor to The Mathieson Alkali Works, Inc., NewYork, N. Y., a corporation of Virginia No Drawing. Application August 151941,

Serial No. 407,071

v 12 Claims. (01 This invention relates to improvements in the picklingof metals and more particularly to pickling inhibitors, i. e., materialswhich retard the rate of reaction of aqueous acid on metals, as inpickling steel. The invention includes not only the improvements inpickling, but also new pickling baths containing the inhibitors.

Inhibitors used in accordance with th invention are sulfur derivativesof higher aliphatic amines and other nitrogen bases, resulting from thechemical combination of sulfur or a sulfur compound in which the sulfurhas a valence lower than six, including sulfur, the polysulfldes, sulfurdioxide, sulfurous acid and its salts, carbon bisulilde, mercaptans,organic sulfides and disulfides, thionyl chloride and other sulfurchlorides, salts of thionic acids. hyposulfurous acid, thiosulfurousacid, and the like, with higher aliphatic amines --or nitrogen bases,including in particular those ggepared by amination of chlorinatedhydrocar- The nitrogen compositions which may be combined with sulfur orone of its lower valence compounds in producing the new compositions arethe amlnated products resulting from the direct amination of chlorinatedaliphatic hydrocarbons such as gasoline, kerosene, gas oil and paraffinwith ammonia.

Products resulting from the treatment of these amines, and particularlythe product resulting from the amination of chlorinated kerosene, as

' described in my'application Serial No. 382,211,

filed March 7, 1941, with sulfur or sulfur dioxide, give outstandingresults as pickling inhibitors. The amines from variou chlorinatedpetroleum fractions such as gasoline. kerosene, gas oil or paraflin maybe employed, either directly as the crude product resulting from theamination, or as products purified by distillation or other knownmethods of purification. or as the residues resulting from thedistillation of such products. moi these materialsiorm hisbly activepicklinl inhibitors when combined with sulfur in a low valence state.and may be used with advantage in practicing this invention.

It requires only a trace of sulfur (or sulfur compound) to import tothese amines pronounced inhibitor activity, although in general thequantity of sulfur or sulfur compound used will be appreciable. Forexample, if a small amount of one of the amines, say a fraction of 1%,is dissolved in a typical acid pickling bath, and is then treated withbut a trace of a soluble low valence sulfur compound, the action of theacid on steel or iron is markedly inhibited. Thus Example 1.-284 partsof the crude amines resultingfrom the amination of a chlorinatedMichigan kerosene containing chlorine as described in my saidapplication Serial No. 382,211,

were treated with 82 parts of sulfur dioxide,

forming 366 parts of reaction product. The amine, which had a molecularweight of about 250, combined with the sulfur dioxide in the ratio of 1to 1.13. The reaction was exothermic and considerable heat was givenoil. The reaction was assumed to be completed when the evolution of heatstopped. The product was a dark viscous oil, soluble in water and havinga slight odor of sulfur dioxide. Addition of alkali liberated theamines. The product was soluble in dilute aqueous acid. Tested bystandard procedure, in a 6% sulfuric acid pickling bath, this productshowed a high inhibiting efilciency. This same product, dissolved in apickling bath containing'15% hyd-rochloric acid again gave excellentresults in inhibiting loss of metal.

Example 2.---Hydrogen' sulfide was passed into 25 parts of the aminedescribed in Example 1 until 3.5 parts of the hydrogen sulfide wereabsorbed, corresponding to a molecular ratio of 1:1. The reaction wassomewhat exothermic. The product was a black viscous oil with anundesirable odor, unstable toward alkali, and somewhat soluble in waterand dilute aqueous mineral acids. It was a good pickling inhibitor foreither sulfuric or hydrochloric pickling baths. Example 3.-28 parts ofthe amine of Example 1 were mixed with 3.6 parts of flowers of sulfurand allowed to stand for several hours. The sulfur dissolved completely.giving a. black viscous oil somewhat soluble in water and dilute aqueousmineral acids and having a high inhibiting eihciency in acid picklingbaths. Very little'heat was generated when the amines combined with thesulfur.

Other products, which, with various sulfur compounds such as thosereferred to above, give pickling inhibitors of high emciency, includethe fraction resulting from the distillation of a crude mine fromchlorinated kerosene at 110-180 C./ mm., a fraction of the same amineboiling at 48-107 0.118- mm., and another fraction of the same amineboiling at 192-208 C ./15-16 mm.

It is not necessary that the sulfur be combined with the amine after theamineis produced. In some cases, effective inhibitors may be directlyproduced from petroleum fractions, such as Michigan kerosene, whichcontain a small amount of combined sulfur. This is illustrated by thefollowing example:

Example 4.A crude amine resulting from the amination of a chlorinatedMichigan kerosene containing some sulfur was heated, in the form of thesulfate, at 200 C. for live hours. The resulting product had excellentinhibiting efficiency. The same amine, without heating or conversion tothe sulfate, was subjected to vacuum distillation giving a distillateboiling at l15-1'75 C./15 mm. and a residue. The distillate had arelatively low efficiency as an inhibitor while the residue, which gavea definite test for sulfur, had a high efliciency.

Instead of heating the sulfate, the same result may be obtained byheating the hydrochloride.

Example 5.-17.4 parts of a crude amine produced from kerosene andcontaining of water were neutralized with 4 parts of 66 sulfuric acidcontaining 0.1% sulfur dioxide. The result-! ing product, whichcontained a small amount of an amine-sulfur dioxide reaction, showed ahigh efficiency as an inhibitor.

While in the foregoing examples, products derived from amines fromkerosene with sulfur,

sulfur dioxide and hydrogen sulfide have been described, it is to beunderstood the various amines described above may be combined with otherlow valence sulfur compounds, sulfur or polysulfides to give otheramine-sulfur products which have high efliciency as pickling inhibitors,and that while in general the best results are obtained when asubstantial proportion of sulfur or sulfur compound is combined with theamine, for example, when there is combined about one atom of sulfur foreach molecule of amine, much smaller proportions of the sulfur or sulfurcompound, downto mere traces, give effective results. The use of largeramounts of sulfur or sulfur compound, even largely in excess of thequantity which will combine, leaving free sulfur or free sulfurcompound, is unobjectionable.

I claim:

l. A pickling bath for metals including a pickling acid, and as aninhibitor, :1. small amount aliphatic hydrocarbon with sulfur in avalence state less than six.

2. A- pickling bath for metals including a pickling acid, and as aninhibitor, a small amount of a, reaction product of an aminatedchlorinated kerosene with sulfur in a valence state less than six.

3. A pickling bath for metals including a pickling acid, and as aninhibitor, a small amount of a reaction product of an aminatedchlorinated aliphatic hydrocarbon with sulfur.

' 4. A picklingbath for metals including apickling acid, and as aninhibitor, a small amount of a reaction product of an aminatedchlorinated aliphatic hydrocarbon with sulfur dioxide.

5. A pickling inhibitor for acid pickling baths for metals comprising areaction product of an aminated chlorinated aliphatic hydrocarbon withsulfur in a valence state less than six.

6. A pickling inhibitor for acid pickling baths for metals comprising areaction product of an aminated chlorinated kerosene with sulfur in avalence state less than six.

7. A pickling inhibitor for acid pickling baths for metals comprising areaction product of an aminated chlorinated kerosene with sulfur.

8. A pickling inhibitor for acid pickling baths for metals comprising areactionproduct of an i aminated chlorinated kerosene with sulfur di-'oxide.

9. The process of pickling metals which comprises exposing the metal toan aqueous acid containing a small amount of reaction product of anaminated chlorinated aliphatic hydrocarbon with sulfur in a valencestate less than 6.

10. The process of pickling metals which comprises exposing the metal toan aqueous acid containing a small amount of reaction product of anaminated chlorinated kerosene with sulfur in a valence state less than6.

11. The process of pickling metals which comprises exposing the metal toan aqueous acid containing a small amount of reaction product of anaminated chlorinated aliphatic hydrocarbon with sulfur.

12. The process of pickling metals which comprises exposing the metal toan aqueous acid containing. a small amount of reaction product of anaminated chlorinated aliphatic hydrocarbon with sulfur dioxide.

CHARLES C. CLARK.

